OBJECTIVE: To analyze factors associated
with intracranial hypertension in pediatric patients who suffered severe head
injuries.METHODS: Retrospective cohort study, with data collected from September
1998 through August 2003, including patients aged 0 to 16 who suffered severe
head injuries, Glasgow score < 9, and submitted to intracranial pressure (ICP)
monitoring (n = 132). Intracranial hypertension (IH) was defined as an episode
of ICP > 20 mmHg requiring treatment, while refractory IH was ICP over 25 mmHg
requiring barbiturates or decompressive craniectomy. Univariate analysis was
followed by multivariate analysis; variables were considered significant if
p < 0.05.RESULTS: Ages ranged from 2 months to 16 years, median age 9.7 (6.0-2.3)
years. Glasgow scores ranged from 3 to 8, median 6 (4-7). Traffic accidents
were responsible for 79.5% of events. Monitoring devices were installed, on
average, 14 hours after trauma, median time 24 hours. One hundred and three
patients (78%) had IH, while 57 (43.2%) had refractory IH. In multivariate analysis,
younger age ranges were associated with IH [relative risk = 1.67 (1.03-2.72);
p = 0.037], and abnormal postures were associated with refractory IH [relative
risk = 2.25 (1.06-4.78)]. The group mortality rate was 51.5%; it was correlated
with use of barbiturates in refractory IH and low cerebral perfusion pressure
at the intensive care unit.CONCLUSIONS: IH and refractory IH were frequent events in pediatric patients
who suffered severe head injuries. The younger the patient, the greater the
chance of developing IH. The presence of abnormal postures was found to be a
risk factor for refractory IH.

Every year, trauma kills 22 thousand Brazilian
children and teenagers.1 Eighty five percent of victims of severe
trauma suffer associated head injury (HI), the injury responsible for most deaths.2,3
The number of survivors with impairments ranges from 3 to 31 for each death.3

After a HI, events such as hypoxemia, intracranial
hypotension and hypertension (IH) cause secondary damage to the encephalon and
are strongly associated with poor results.4 Patient interventions
focus on preventing and correcting such factors, with the goal of ensuring the
supply of oxygen to the encephalon. Measures taken to that end include controlling
intracranial pressure (ICP) and maintaining cerebral pressure perfusion (CPP).

Intracranial hypertension can lead to decreased
pressure perfusion, limiting or stopping blood flow and causing neuronal death.5
It can also kill through herniation of intracranial structures. Clinical evaluations
have been known to be an unreliable parameter for IH detection for over 80 years.6
Using only this criterion, IH is only detected in advanced stages, when there
is already intense suffering or when herniation and death are inevitable.

Several authors associate IH with poor neurological
outcomes or higher mortality rates.7,8 Monitoring ICP and aggressive
treatment for IH have also been associated with better outcomes in the literature
about pediatric patients with severe head injuries.9,10

However, pediatric guidelines recommend monitoring
ICP in children and teenagers with severe head injuries in cases of class III
evidence, uncertain level of clinical safety or therapeutic option.11

Studies have sought factors related to intracranial
hypertension, but mostly among adults or in samples with few children.4,12
We need more pediatric studies to determine factors for identifying which patients
might benefit from ICP monitoring and which could be spared of its risks, complications,
and expenses.

The objective of this study was to analyze factors
associated with IH in children and teenagers who suffered severe head injuries,
hospitalized at intensive care units.

Methods

This was a retrospective cohort study, with data
collected from September 1998 through August 2003. It included patients aged
0 to 16 admitted to the pediatric intensive care unit (ICU) of Hospital João
XXIII (HJXXIII) because of severe blunt trauma to the head (score below 9 in
the Glasgow coma scale) and submitted to ICP monitoring. Exclusion criteria
included penetrating injuries caused by firearms, blades or other objects, as
well as teenagers with severe HI admitted to the adult ICU, due to differences
in behavior and protocols.

HJXXIII is a public school hospital located in
Belo Horizonte, capital city of Minas Gerais, a state in Southeastern Brazil.
The metropolitan region is home to approximately 5 million inhabitants. The
hospital belongs to Fundação Hospitalar do Estado (State Hospital
Foundation); it features 400 beds, and is considered a reference for urgent
and emergency cases. On average, it treats 13 thousand patients per month, 4
thousand of which are children and teenagers (33%). Of those, 310 are admitted
to the hospital every month, and 250 are admitted to the pediatric ICU every
year.

The treatment of pediatric ICU patients uniformly
followed a protocol based on the 1995 guidelines for treatment of severe head
injuries.13 The protocol was published in a review article14
and reviewed when the guidelines were published in 2000.15

The study was approved by the Research Ethics
Committee of Universidade Federal de Minas Gerais (UFMG), Belo Horizonte (Minas
Gerais, Brazil), under protocol ETIC 420/04.

The data were collected from patients' records
at the hospital's Medical Archive and Statistics Service for the period between
September 1998 and February 2002. Since then, the data were collected at the
bedside, after obtaining free and informed consent.

Intracranial hypertension was defined as an episode
of ICP above 20 mmHg and requiring treatment; patients were treated if ICP remained
at least 5 minutes above said value.16

Refractory intracranial hypertension was defined
as an episode of ICP sustainably above 25 mmHg and requiring barbituric coma
or craniectomy after ruling out mass lesions with surgical indication.11

Head injury severity was measured according to
the Glasgow Coma Scale (GCS).17 Children under the age of 4 were
assessed by verbal and motor response adapted to their age.3,18 Patients
were considered victims of severe HI if they still scored 8 or less in the GCS
6 hours after the trauma.

Patients with abnormal flexion or extension postures
were grouped for an analysis of correlation with occurrence intracranial hypertension.12

Tomographic findings were collected in a single
group of traumatic brain injuries with greater probability of developing IH
(hemorrhages, hematomas, injuries, edema, edema and swelling, cistern compression
or obliteration) and another with lower probability [normal tomography or
tomography showing diffuse axonal injury (DAI)].12

Circulatory shock upon first admission was defined
as presence of systolic blood pressure below the fifth percentile for the relevant
age, or a weak pulse and capillary ballooning above 2 seconds, as long as there
are corrective measures, such as volume replacement or use of vasoactive medication.

Trauma severity was assessed by the Pediatric
trauma scale (PTS).19 The following associated injuries were considered:
injuries to the spinal column and medulla, thorax, abdomen and musculoskeletal
system.

Infections to the central nervous system were
considered if diagnosed and treated by attending physicians based on clinical
suspicion and whatever complementary test they requested.

The data was analyzed using the computer application
Epi-Info. Comparisons between proportions used the chi-square test, and Fisher's
exact test when one or more quads had an expected value below 5. The linear
trend chi-square test was used in situations featuring progression. Relative
risk (RR) and its 95% confidence interval were also calculated. RR is noted
as a value followed by confidence interval in parentheses.

Variance analysis was used to compare means for
data with normal distribution, but the Kruskal-Wallis nonparametric test was
used in cases in which variances were not homogeneous and were expressed in
terms of medians and 25-75% inter quartile range (25-75 IQ). Variables with
p < 0.25 in univariate analysis were analyzed simultaneously by logistic
regression used for multivariate analysis, using computer application MULTLR.
The final model considered as significant all remaining variables with value
p < 0.05.

Results

Between 1998 and 2003, the pediatric ICU had
eight beds and received circa 1,000 patients; 315 had blunt head injuries and
191 had GCS scores below 9. Of those, 132 received ICP monitoring and were included
in this study.

Patient age ranged from 2 months to 16 years,
with median age 9.7 (6.0-12.3) years. The most common trauma mechanisms were
being run over by a car (51.5%), injuries in automobile passengers (18.2%),
to bicycle riders (9.8%), falls (13.6%), assault (1.5%), and others or not informed
(3%).

Most patients had multiple intracranial lesions
(330 lesions in 132 patients). The most common were swelling, found in 74 patients
(56.1%); DAI, found in 56 (42.4%); contusion or intraparenchymal hemorrhages,
found in 46 (34.8%); and subarachnoid hemorrhages, found in 41 (31.1%).

GCS scores ranged from 3 to 8, with a median
of 6 (4-7). PTS scores ranged from -3 to 11, with a median of 4. One hundred
and twelve major associated injuries were diagnosed: 48 thoracic, 37 musculoskeletal,
21 abdominal, and 6 of the spinal column and medulla.

IH and associated factors

One hundred and three patients monitored (78%)
had at least one IH episode requiring treatment, and 57 (43.2%) had refractory
IH episodes.

Table
2 shows the univariate analysis of refractory IH frequency. In this analysis,
the factors sex, age and presence of abnormal postures were associated with
the occurrence of events, but they were then submitted to multivariate analysis
to verify the association.

The correlation between age and occurrence of
IH and refractory IH was analyzed using the linear trend chi-square test. Table
3 shows that, compared to teenagers, the younger the patient, the greater
the chance of IH. The same analysis was performed for refractory IH without
finding significant statistical differences (Table
4).

No kind of associated injury showed greater risk
of developing IH.

Multivariate analysis

Multivariate analysis demonstrated that younger
age was related to higher probability of IH [RR = 1.67 (1.03-2.72); p =
0.037]. All children younger than 1 year old suffered IH. The presence of
tomographic changes was not significantly associated with IH [p = 0.08;
RR = 2.78 (0.88-8.76)].

On average, ICP monitoring devices were installed
14 hours after trauma, but 50 percent of patients were monitored after more
than 24 hours, while 5% were monitored after more than 48 hours.

One hundred and five (79.5%) patients were monitored
using a subdural or subarachnoid Richmond screw, 19 (14.4%) with intraparenchymal
fiber optics, 6 (4.6%) with intraventricular catheters, and 2 (1.5%) with subdural
catheters.

After finding normal ICP, the subdural screw
malfunctioned in three patients. Based on clinical and tomographic assessments,
monitoring was withdrawn.

Almost 80 percent of patients had at least one
IH episode. This piece of data is of questionable relevance, since there is
no evidence that ICP slightly above 20 mmHg is more harmful than some of the
measures used to control it.20

However, after observing that over 40 percent
of patients had refractory IH, excluding those with surgical indication for
mass effect lesions, the number is worrisome. The literature recognizes that
morbidity and mortality are very high for refractory IH patients,11,21
but also that the benefits of the measures used to control it are even more
questionable.11,22,23

Thus, in light of current knowledge, having children
and teenagers with severe head injuries exposed to risk of more than 40 percent
of developing undocumented refractory IH is unacceptable, but so is instituting
aggressive treatments without their need being certain.11

In this study, half of all patients were monitored
more than 24 hours after the injury. This may have contributed to the high rates
of IH, since we know that sustained IH leads to a vicious circle of ischemia,
edema and worsened IH.24

The study showed higher rates of IH in younger
children. Despite the small number of children younger than 1, they had the
highest rates of IH. The data reinforce the importance of monitoring in this
age range and counter the argument that such patients are under lower risk of
developing IH because of their open fontanelles and unconsolidated sutures.11

The importance of monitoring small children increases
with reports that children younger than 4 who suffer head injuries have worse
prognoses than older ones.7 This study is one of the few to document the occurrence
of refractory IH in infants and small children.10

Patients who suffered severe head injuries and
have tomographic changes also had high rates of IH, as expected.2
However, unlike what has been described for adults, the group with isolated
DAI also had high rates of IH. The results were similar to Esparza et al.'s
pediatric study.25,26

The difference in event rates in children may
be explained by the higher ratio of cranial content and higher frequency of
swelling compared to adults.9

The study's methodological limitations may have
influenced the results. Diagnoses of tomographic lesions made by the neurosurgeons
at the emergency service may be inaccurate. This is even more relevant when
considering tomography in children. Retrospective data collection was another
study limitation.

Circulatory shock did not influence the occurrence
of IH or refractory IH, unlike the findings from Narayan et al., in which the
association of hypotension with being 40 years old or more or to abnormal postures
was associated with higher rates of IH among adults who suffered head injuries.12
The result may be attributed to the criteria used in this study for including
patients with signs of shock, but not hypotension; this would lead to the cerebral
blood flow being less compromised and, consequently, to less ischemia and swelling.

The presence of abnormal postures was correlated
to the occurrence of refractory IH, even after multivariate analysis. The result
is incredibly important, since it means ICP monitoring is recommended for pediatric
patients with abnormal postures even with normal tomography and hemodynamic
stability, contrary to what is recommended for adult patients.12
Bruce et al. are among the few authors to correlate IH in children with the
presence of abnormal postures.27

Less than 8 percent of monitored patients had
CNS infections; all of them had good outcomes, as the literature would lead
us to expect.12 No prophylactic antibiotics were used while the devices
were installed, and there was no difference in rates of infection for patients
with and without monitoring devices.11

Three quarters of patients were monitored using
a Richmond screw. Subarachnoid monitoring, either by screw or by catheter, seems
to be a cheap option, with easy installation and accessible in locations with
fewer resources,28 especially considering how hard it is to install
ventricular catheters in trauma patients and how expensive fiber optics and
catheter tip sensors can be.

In three cases in this study, the screw initially
showed normal ICP and then stopped working. Physicians chose to keep those patients
unmonitored from then on based on clinical and tomographic assessments. In this
analysis, those three patients are listed as having no ICP increases. However,
this study limitation does not bias it towards higher rates of IH.

The absence of hemorrhagic complications secondary
to ICP monitoring requiring surgical interventions matches the literature. Significant
hematomas requiring surgical removal were found in only 0.5 percent of patients.
Clearly, there is a greater risk of coagulation conditions.29

In 2005, Carvalho studied the group's elevated
mortality rate,30 which may have been secondary to the high frequency
of refractory IH and the use of barbiturates at the time.

Conclusions

IH and refractory IH were frequent events in
pediatric patients who suffered severe head injuries, independently of the presence
of risk factors accepted for adult patients.
The younger the patient, the greater the chance of developing IH. The presence
of abnormal postures in pediatric patients who suffered severe head injuries
was found to be a risk factor for refractory IH.

Criteria for ICP monitoring in Pediatrics should
be different than those used for adults. The infectious and hemorrhagic complications
of monitoring have little clinical significance, and they are at least five
times less risky than refractory IH.

Acknowledgements

We would like to thank the professionals at Hospital
João XXIII and at the UFMG School of Medicine Graduate Program; and professors
Maria do Carmo Barros de Melo (UFMG) and Eduardo Juan Troster (USP) for their
valuable suggestions and corrections.